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                  <p class="p_Heading1"><span class="f_Heading1">Data Flow Diagrams</span></p>



  
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                <p class="p_BodyText"><span class="f_BodyText">The following text is derived from the <a href="http://en.wikipedia.org/wiki/Data_flow_diagram" target="_blank" class="weblink">Data Flow Diagram</a> entry in the online Wikipedia.</span></p>
<p class="p_OMGText" style="margin: 5px 0px 5px 48px;"><span class="f_OMGText">A data flow diagram (DFD) is a graphical representation of the &quot;flow&quot; of data through an information system. A data flow diagram can also be used for the visualization of data processing (structured design). It is common practice for a designer to draw a context-level DFD first which shows the interaction between the system and outside entities. This context-level DFD is then &quot;exploded&quot; to show more detail of the system being modeled.</span></p>
<p class="p_OMGText" style="margin: 5px 0px 5px 48px;"><span class="f_OMGText">Data flow diagrams were invented by Larry Constantine ... based on Martin and Estrin's &quot;data flow graph&quot; model of computation. [They] are one of the three essential perspectives of Structured Systems Analysis and Design Method SSADM. The sponsor of a project and the end users will need to be briefed and consulted throughout all stages of a system's evolution. With a dataflow diagram, users are able to visualize how the system will operate, what the system will accomplish, and how the system will be implemented. The old system's dataflow diagrams can be drawn up and compared with the new system's dataflow diagrams to draw comparisons to implement a more efficient system.</span></p>
<p class="p_OMGText" style="margin: 5px 0px 5px 48px;"><span class="f_OMGText">Developing a DFD helps in identifying the transaction data in the data model.</span></p>
<p class="p_BodyText"><span class="f_BodyText">For further information on the concepts of Data Flow Diagrams, refer to the <a href="http://en.wikipedia.org/wiki/Data_flow_diagram" target="_blank" class="weblink">Wikipedia</a> item and its linked sources.</span></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">Data Flow Diagrams in Enterprise Architect</span></p>
<p class="p_BodyText"><span class="f_BodyText">Enterprise Architect enables you to develop Data Flow diagrams quickly and simply, through use of an MDG Technology integrated with the Enterprise Architect installer. The Data Flow diagram facilities are provided in the form of:</span></p>
<ul style="text-indent: 0px; margin-left: 30px; list-style-position: outside;">
<li><span class="f_Bulletlist1">A Data Flow diagram type, accessed through the </span><span class="f_UIControl"><a href="newdiagrams.htm">New Diagram</a></span><span class="f_Bulletlist1"> dialog</span></li>
<li><span class="f_Bulletlist1">A </span><span class="f_UIControl">Data Flow Diagram</span><span class="f_Bulletlist1"> page in the Enterprise Architect UML </span><span class="f_UIControl">Toolbox</span></li>
<li><span class="f_Bulletlist1">Data Flow element and relationship entries in the </span><span class="f_MenuKeyField"><a href="umltoolboxshortcutmenu.htm">UML Toolbox Shortcut</a></span><span class="f_Bulletlist1"><a href="umltoolboxshortcutmenu.htm"> Menu</a> and </span><span class="f_UIControl"><a href="quick_links.htm">Quick Linker</a></span><span class="f_Bulletlist1">.</span></li>
</ul>
<p class="p_SubHeadingL2"><span class="f_SubHeadingL2">Data Flow Diagram Toolbox Page</span></p>
<p class="p_BodyText"><span class="f_BodyText">You can access the </span><span class="f_UIControl">Data Flow Diagram</span><span class="f_BodyText"> page of the </span><span class="f_UIControl">Toolbox</span><span class="f_BodyText"> through the </span><span class="f_MenuKeyField">More tools | Data Flow Diagrams</span><span class="f_BodyText"> menu option. The following icons are available:</span></p>
<p class="p_TextIndentedL2"><img src="data%20flow%20tools.png" width="151" height="130" border="0" alt="Data Flow Tools"></p>
<ul style="text-indent: 0px; margin-left: 30px; list-style-position: outside;">
<li><span class="f_Bulletlist1" style="font-style: italic;">Process</span><span class="f_Bulletlist1"> is a process or activity in which data is used or generated</span></li>
<li><span class="f_Bulletlist1" style="font-style: italic;">External</span><span class="f_Bulletlist1"> represents an external source, user or depository of the data</span></li>
<li><span class="f_Bulletlist1" style="font-style: italic;">Data Store</span><span class="f_Bulletlist1"> represents an internal physical or electronic repository of data, into and out of which data is stored and retrieved</span></li>
<li><span class="f_Bulletlist1" style="font-style: italic;">Data Flow</span><span class="f_Bulletlist1"> (connector) represents how data flows through the system, in physical or electronic form</span></li>
<li><span class="f_Bulletlist1" style="font-style: italic;">Gate</span><span class="f_Bulletlist1"> represents the termination point of incoming and outgoing messages on a lower level diagram (that is, messages to and from processes depicted elsewhere).</span></li>
</ul>
<p class="p_BodyText"><span class="f_BodyText">When dragged onto a Data Flow diagram, the elements and relationship have the following appearances:</span></p>
<p class="p_TextIndentedL2"><img src="example%20of%20a%20data%20flow%20diagram.png" width="767" height="596" border="0" alt="Example of a Data Flow Diagram"></p>
<p class="p_BodyText"><span class="f_BodyText">To preserve the simplicity and readability of the diagram, you cannot display the element compartments on the diagram.</span></p>
<p class="p_SubHeadingL2"><span class="f_SubHeadingL2">Context Diagram</span></p>
<p class="p_BodyText"><span class="f_BodyText">A </span><span class="f_BodyText" style="font-style: italic;">Context</span><span class="f_BodyText"> diagram is a top-level Data Flow diagram that has just one Process element representing the system being modeled, showing its relationship to external systems.</span></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">Disable Data Flow Diagrams</span></p>
<p class="p_BodyText"><span class="f_BodyText">If you prefer not to use Data Flow Diagramming in Enterprise Architect, you can disable it (and subsequently re-enable it) using the </span><span class="f_UIControl"><a href="manage_mdg_technologies.htm">MDG Technologies</a></span><span class="f_BodyText"> dialog (</span><span class="f_MenuKeyField">Settings | MDG Technologies</span><span class="f_BodyText">).</span></p>




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